Why did Constantine move the capital of the Roman Empire?

This is a question that gets asked from time to time. When people look back in history and ponder why the capital was moved from the capital of the known world, it can be challenging to figure out why. So, why did Constantine move the capital of the Roman Empire? There are several reasons, including location, protection of the provinces, population, trade and finance, familiarity, and family. Let’s look at these reasons more closely.

We need to examine Constantine’s earlier life before he became emperor to understand some of his possible motives.

Constantine was born in Naissus (modern-day Niš, Serbia) in AD 272. He was the son of the future emperor Flavius Constantius (Constantius I) and Helena, a Greek woman who was also a Christian. She is also known as Saint Helena. Flavius Constantius was born in the same region, while Helena was from Bithynia in Asia Minor.

In AD 285, Emperor Diocletian appointed Maximian as his co-emperor, with Maximian ruling in the west and Diocletian in the East. Maximian ruled from Mediolanum (Milan, Italy) and Augusta Treverorum (Trier, Germany). In contrast, Diocletian ruled from his palace in Nicomedia (İzmit, Turkey). This was to help manage an already vast empire. Further reforms by Diocletian brought about what we now know as the Tetrarchy – where two junior emperors, or Caesars, would help rule the empire alongside their senior emperor, or Augustus. Here, Flavius Constantius was appointed as Maxmian’s Caesar in the West.

Upon this appointment, Constantine was sent to live in the eastern court of Diocletian, where he learned all things Latin and Greek. As he got older, he fought for Diocletian and Galerius (Diocletian’s Caesar) with distinction, gaining military promotions.

In AD 305, Diocletian and Maximian both abdicated, with Constantius and Galerius being promoted to Augusti. Severus and Maximinus became the junior Caesars. Constantine was conspicuously overlooked.

Constantine fled the eastern court in AD 305, linking up with his father, Emperor Constantius, in the west at Eboracum (York, England).

Events unfolded over the following years, ending in Constantine becoming the sole emperor of a re-united Roman Empire, where he started his reforms earnestly. One of his earliest reforms was to stop the Christian persecutions that had begun under Diocletian. He also decreed that Christianity and Christians would be tolerated within the empire, a marked shift in policy from previous emperors.

There are several reasons why Constantine might have moved the capital from Rome to the then-Thracian city of Byzantium.

Let’s look at the geographical location of Byzantium/Constantinople (modern-day Istanbul, Turkey). The city straddles Europe and Asia on the edge of the Bosphorus. It is closer to the geographical center of the Roman Empire, with provinces in Syria and the Middle East counterbalancing the traditional western provinces of Gaul and Hispania.

Having the capital located here enables the emperor to respond to crises in the West and East more efficiently. Rome was sufficient when the empire mainly revolved around the western provinces. However, further moves east made Rome less practical, particularly for a sole emperor.

By having the capital in Constantinople, Constantine and future emperors could have launched more efficient eastern campaigns, with most forces able to launch from Asia Minor instead of marching across Western Europe.

Moving the capital to Constantinople enabled Constantine to respond more effectively to barbarian incursions. The Danube frontier was always problematic for the Romans, but with more and more barbarian hordes bearing down on the Danube border in modern-day Bulgaria and Serbia, better protection was needed. It also allowed for a better defensive position in case of an invasion from the East into Europe.

It must be noted that by this time, Constantine had reformed the Roman army and had moved away from the legionary cohorts, introducing the Limitanei and Comitatenses troops. The limitanei were the border troops posted along Rome’s borders. They were lightly armored (at least compared to the comitatenses troops) and were the first line of defense for the empire.

The comitatenses were the field army troops, able to move around the empire’s lands. They were the empire’s heavy infantry and better equipped than the limitanei.

Deploying troops from a command in Rome would have meant delays in mobilizing armies and legions, which would have required them to cover a much larger distance to reach their required locations.

The navy also built its base around the Golden Horn (which fed into the Bosphorus). This was important positioning as it allowed for a quick response if enemies decided to sail up the narrow strip of water.

The navy base was also protected, with a large chain stretching from one side of the Golden Horn to the other that could be raised to stop enemy ships from continuing their journey.

At the time of the move, the population of the western provinces began to stagnate, with some areas declining in population size. The same could hardly be said for Rome itself. The eastern provinces were still growing, and they had further opportunities for growth when new lands were conquered.

Trade growth allowed the populations in the eastern provinces to grow, while the populations in the western provinces had already reached maturation. The East offered more in terms of growth than anything they could gain from east of the Rhine border.

When you base yourself on the cusp between two continents, you have put yourself in a prime place to trade. As a significant trading city, Constantinople was able to take advantage of the booming trade between the East and West. Acquiring spices and silks from the East only added to the prestige of the new Roman capital.

At this time in history, the eastern provinces were also much wealthier than their western counterparts. This is largely due to the trade mentioned above. When a trading hub is closer to where people want to sell, it will attract a lot more people wanting to sell.

Constantinople also controlled the Bosphorus, the narrow strip of water that separated Europe and Asia. This meant that it controlled a valuable sea route for trade in and out of the Black Sea, which was critical for the ancient civilizations that bordered it.

Constantine’s early days were spent in Nicomedia, on the other side of the Bosphorus. This would have been very familiar territory to Constantine and almost like home. He spent more time in this region than he did in Rome itself. He spent his youth there, getting an education and fighting for Diocletian and Galerius while based in Nicomedia. It wasn’t until he was in his 30s that he fled the eastern court to link up with his father in Britannia.

His mother was born in Bithynia, a province of Asia Minor that Nicomedia was the capital of. It is believed she was born in the town of Drepanon. Constantine later changed its name to Helenopolis. However, her actual birthplace is a source of dispute.

While Constantine moved the empire’s capital to the East, the heart of this ancient civilization remained in the Eternal City.